Pluto, a lonely outpost first spotted 85 years ago and wrapped in mystery ever since, has been visited at last, and the previews are stunning.
On Tuesday night, engineers with NASA’s New Horizons mission confirmed their spacecraft has survived its whirlwind tour of Pluto and its five moons and is now on its way out to the stars.
The encounter marks the culmination of a decade-long $720-million (U.S.) journey that has taken New Horizon to the remote, dimly lit fringes of the solar system and lifted the veil on its most enigmatic world. The probe will never return, but its achievement has left an indelible mark – it is a historic first that mission scientists say links New Horizons directly to the golden age of the space program.
“We were inspired by the Apollo era and we hope this is an Apollo moment for a new generation,” said Richard Binzel, a professor of planetary science at Massachusetts Institute of Technology and a co-investigator with New Horizons team.
Even as they await the best images from the close encounter, scientists are agog over the increasingly detailed and tantalizing glimpses of Pluto and its largest moon, Charon, that were acquired in the days leading up to the long-anticipated rendezvous.
They include the sharpest views yet of a prominent heart-shaped region that straddles Pluto’s equator like a planet-sized Valentine.
While the true nature of the feature is not yet known, its smooth appearance and ragged edge suggest that it consists of frozen gases, possibly including nitrogen, methane and carbon monoxide that solidified out of Pluto’s tenuous atmosphere.
Colour images that the spacecraft beamed to Earth on Monday and were released on Tuesday afternoon suggest there are subtle differences across the heart, further bolstering the idea that Pluto’s surface consists of a lightly cratered terrain partly buried or altered by the transport of volatile gases that are alternately vaporized by sunlight and then refrozen in the extreme cold.
“This is clearly a world where both geology and climatology play a role,” Alan Stern, the mission’s principal investigator, said.
Launched in 2006, New Horizons was designed to complete our first look at the solar system’s original nine planets – as the term “planet” was understood then. More importantly, scientists said, it is the first effort to explore a poorly understood domain beyond the orbit of Neptune where thousands of icy bodies, some nearly as large as Pluto, harbour clues to the solar system’s formation and history.
The first indication that New Horizons succeeded in its quest was picked up by NASA’s Deep Space Network on Tuesday at about 9 p.m. ET. The signal was relayed to the mission’s operations centre at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
Mission team members broke into smiles of relief and then cheered as the status of the spacecraft was confirmed. The excitement was quickly amplified by an auditorium of full of hundreds of scientists, officials and well wishers on hand to watch the drama unfold.
“We have a healthy spacecraft and we’ve recorded data from the Pluto system,” said mission operations manager, Alice Bowman, then, over the growing applause: “We did it!”
In attendance were Alden and Annette Tombaugh, the adult children of astronomer Clyde Tombaugh, who discovered Pluto in 1930 and who died in 1997. A small quantity of his ashes are aboard New Horizons and will leave the solar system with the spacecraft, the first human remains to do so.
As planned, New Horizons’ first contact after the Pluto encounter lasted less than 20 minutes, but it allowed mission controllers to verify that the spacecraft is functioning well. Scientists hope its computer memory is loaded with data that can be reconstituted into dazzling images taken during the closest approach.
Those images are scheduled to start streaming down from New Horizons on Wednesday morning. The probe is so far from Earth and its signal so weak that engineers project it will take until October of next year to download all the data it gathered during the past 48 hours.
The best views of Pluto that New Horizons will ever get should include a sequence of stereo close-ups taken as a strip across the heart-shaped area, providing information about elevation differences and revealing features less than 100 metres in size.
The probe’s spectacular revelations about a complex and varied surface is in keeping with hints that date back to the 1950s, when astronomical observations revealed that Pluto’s brightness changes with a predictable cycle as it rotates every 6.39 days.
In the 1980s, a series of mutual eclipses between Pluto and Charon allowed researchers to build up a crude map of light and dark patches on the surface of both bodies.
Decades later, that map seems to match up well with the more detailed views New Horizons is providing, Dr. Binzel said, with the brightest area seen on Pluto back then corresponding to the heart-shaped region revealed in recent days.
Dr. Binzel added that a Tuesday morning gathering of the science team to examine and discuss the latest images was a celebration as much it was a technical discussion.
“We have come a long way to see how interesting Pluto is and it has not disappointed,” he said.